1. Field of the Invention
The field of the present invention is that of turbomachines and, more particularly, that of the devices for attaching the turbomachines to the aircraft that they propel.
2. Description of the Related Art
An engine, such as a turbojet or turboprop engine may be mounted at various points on the aeroplane, by attachment to a pylon or strut belonging to the aeroplane structure. It may thus be suspended under the wing structure, fixed to the fuselage or mounted in the tail assembly using appropriate means of attachment. These attachment means have the function of transmitting mechanical load between the engine and the structure of the aeroplane. The loads to be taken into consideration are notably the weight of the engine, its thrust, and any lateral aerodynamic loadings. The loads to be transmitted also comprise, amongst other things, the need to react the rotational torque about the axis of the engine.
One method of suspension is to attach the engine to a strut belonging to the structure of the wing of the aeroplane using a forward suspension device and a rear suspension device. The forward suspension, for example in the case of a turbofan engine, is then fixed to the intermediate casing downstream of the fan casing and the rear suspension to the primary flow exhaust casing. These two components in fact constitute the structural elements of a turbomachine, by which all forces are absorbed.
Modern turbojet engines are double flow turbomachines with a high bypass ratio, the secondary or bypass air stream being compressed by a single compressor stage known as the fan. On leaving this stage it is guided by a duct directly into a nozzle to contribute to the thrust of the engine. It thus flows between the main spool of the engine, delimited by casings, and a cold stream duct (generally denoted by its English-language acronym OFD which stands for Outer Fan Duct). This duct is fixed to the engine by connections situated at its two longitudinal ends, a first fixing being upstream on the intermediate casing and a second at the rear on a support ring borne by the exhaust casing.
At its external radius, the intermediate casing generally has two flanges to which the fan casing is fixed at the upstream end and the outer fan duct is fixed at the downstream end. Positioned between these two flanges are localized reinforcements on which a yoke is mounted, forming a means of suspending the engine, and providing the connection with the aircraft and allowing the transfer of the abovementioned loadings. This yoke, as depicted in FIG. 1, is truly yoke-shaped with a rigid central structural part and two pads mounted with the freedom to rotate at the ends of this structural part so as to allow any deformation or movement of the engine in use on the aircraft. It is generally protected from the external elements by a heat shield which envelops it and which provides a barrier against the spread of any engine fire towards the aircraft.
In the conventional way, this heat shield is formed of several elements, in the form of panels, which are assembled with one another and fixed to the suspension yoke. Bearing in mind the way the flanges of the intermediate casing and of the outer fan duct evolve during use, these flanges can sometimes impact on one of the elements that forms the heat shield of the yoke, and this is prejudicial to its life. Moreover, removing the heat shield is a relatively complex task and cannot always be performed with the engine installed on the aeroplane, and this means that the engine has to be taken off in order to perform maintenance on this heat shield.
It is an object of the present invention to alleviate these disadvantages by proposing a heat shield device for an engine suspension means that is easy to remove and allows the requisite movements of the flanges of the intermediate casing and of the outer fan duct without the risk of damaging the heat shield associated with this means, or of reducing the fire protection afforded.